Morphology and molecular characterisation of 'Echinochloa' species in the northern grain region

The genus 'Echinochloa' includes two species listed in the top five worst weeds of agricultural crops. 'E. crus-galli' (L.) Beauv. and 'E. colona' (L.) Link, are major summer grass weeds in farming systems of the northern grain region of Australia including dryland cotton, sorghum and fallows. A 2001 survey indicated varied levels of control of these species, with no farmers reporting good control in sorghum and only 38% reporting good control in cotton. Given the variability in control reported by farmers, a detailed knowledge of variability within, as well as among, populations and species of 'Echinochloa' would be useful in directing appropriate management strategies. Currently little is known about the genetic structure of this genus in Australia and the existence of morphologically intergrading types complicates species identification and diversity studies. The development of genetic markers for the measurement of genotypic variation has assisted in resolving taxonomic uncertainties and providing information on population diversity of many plant species. This study reports on the use of molecular techniques, including microsatellites (SSRs), together with classic morphological taxonomy to investigate the genetic diversity of 'Echinochloa' species from a field to a regional level.